Electromagnetic operator



Feb. 17, 1953 B. FORMAN ELECTROMAGNETIC OPERATOR Filed Aug. 15, 1950 a,i a 5 o0 Q wmowowowowom l Szraie.

IN V EN TOR.

n 4 Z 5 M f Patented Feb. 17, 1953 ELECTROMAGNETIC OPERATOR Louis B.Forman, Detroit, Mich., assignor to Chrysler Corporation, Highland Park,Mich., a

corporation of Delaware Application August 15, 1950, Serial No. 179,448

My invention relates to electromagnetic operators and more particularlyto the type commonly known as solenoids.

The present invention ha particular reference to a solenoid. utilizedfor controlling valving in a fluid pressure system where a substantialforce is needed to open the valve.

A principal object of my invention is to provide an improved. solenoid.which is capable of delivering a greater force at the beginning of itsstroke compared. to the remainder of its stroke relative to those knownin the art.

Another object of my invention is to provide an improved solenoid whichis easily as well as economically manufactured.

Other objects and advantages will become more apparent from thefollowing description of one embodiment of my invention, reference beinghad to the accompanying drawings in which:

Fig. 1 is a sectional view of a fluid pressure system illustrating theapplication of my improved. solenoid thereto.

Fig. 2 is a sectional view of a portion of the structure shown in Fig. 1illustrating the change in the structure when my improved solenoid isenergized.

Fig. 3 is a sectional View of the solenoid shown in Figs. 1 and 2illustrating the internal construction thereof.

Fig. 4 is a diagrammatic view of the forcestroke relationship of aconventional solenoid and my improved solenoid.

In Fig. l I have shown an application of my improved solenoid to a fluidpressure system which controls the operation of the motor vehicletransmission. system is more fully described and claimed in thecopending application of William A. Hunter, Serial No. 740,425 filedApril 9, 1947 and is shown merely for illustration of one application ofmy invention. The motor vehicle transmission is represented merely by ashift sleeve A which effects different speed ratios when moved by thefluid pressure system, generally designated by the letter B. In Fig. 1 Ihave illustrated servomotor mean-s in the form of a fluid motor or shiftcylinder C. For controlling the shift of sleeve A, this motor comprisesa cylinder I slidably re-= ceiving a piston II which slidably receives arod I2 which is mounted to reciprocate in the guideways I3 and I l.Fixed to this rod is the collar I5 of a yoke I6 connected with sleeve Ato effect shift thereof. A relatively small force preloaded engagingspring I1 is threaded on the rod I2 and is disposed between piston I Iand yoke IE to provide a lost motion thrust transmitting section suchthat piston II may move forwardly or to the left for its power stroke,being limited by relief ports I8 and abutment I9 in advance of the fullclutching shift of the sleeve A. In the position of the piston I I, asshown in the drawing, the engaging spring I1 is compressed and thiscompressed spring then urges the yoke collar I5 The subject fluidpressure 0 1 Claim. (Cl. 175-336) towards the left so that the sleeve Ais moved into engagement with a blocker 20 and, after coast, with teeth2| and pinion 22. The yoke collar I5 abuts against the rear end ofguideway I3 when the sleeve A has come to rest in its fully engagedupshift position. A kickdown spring 23 is disposed between abutment I9and piston II and serves to return the piston and sleeve A to a positionwhere the piston II engages the guideway It. The spring 23 is thusadapted to effect disengaging movement of the sleeve A relative to theteeth 2I. Ports I8 constitute relief ports to prevent pressure, inexcess of that required to operate the piston, building up in thehydraulic system. At the same time ports I8 serve as a pistonpositioning means and eliminate the need for additional piston abutmentmeans. Ports I8 are uncovered just prior to engagement of the piston I Iwith abutment means I9, therefore, the pressure against the piston isautomatically reduced and the piston is not rammed against the abutmentI9.

The rod I2 has a shoulder 25 which engages the face of the piston whenthe piston is in its furthest rightward position but which, when thepiston and rod are moved to the end of their forward strokes, as shownin Fig. 1, is spaced rearwardly of the piston to provide a gap 25 equalto the distance of the strokes of the piston and rods. This gap isutilized to close an ignition control switch D for interrupting theengine ignition system which is connected through this switch. Piston IIis provided with an annular groove 26 formed in its skirt to define thecam portion 21 which operates the ball actuator 28 for closing switch D.

The pressure fluid supply system has been diagrammatically shown in Fig.1 and comprises a suitable supply 29 of oil which is usually in theengine transmission sump. A pump 30 draws the oil from the supply 29 fordelivery under pressure through pipe 3| hence to the passage 32 undercontrol of a ball valve E. When the valve E is closed, as shown in Fig.1, the oil is fed directly from the pump 30 through pas-sages 3I and 32to shift cylinder B where it moves the piston II and shift rod I2 to theleft thus causing yoke I6 to shift sleeve A to effect a change speedratio of the vehicle transmission.

Valve E is closed by the spring pressure of a valve spring and thepressure of the fluid medium when a solenoid F located above the ballvalve is de-energized and the solenoid plunger extension GI is in itsretracted position as shown in Fig. 1. When the solenoid F is energized,as shown in Fig. 2, the plunger extension II is extended and ball valveE is opened by being forced downwardly off valve seat 42 so that oil nowflows from the pump 30 through the line 3| to open valve E and back tothe supply sump via the return line 43. The open valve E preventssufficient pressure developing in the system to move acaaoor the pistonII against force exerted by the piston retaining spring 23.

Referring now more particularly to Fig. 3, the solenoid F comprises acylindrical casing 50 which is provided at its lower end with a threadedsleeve I for securing the solenoid to the wall 52 of the transmissioncontrol assembly. A coil 53 of cylindrical configuration is disposedwithin the casing 50 and is supported therein by a cup-like member 54having a cover 55. The coil 53 is spaced from the bottom of the cup-likemember 54 by a disc 56. The coil 53 is connected by wires 200 to anappropriate electrical circuit and is providecl with a centrally locatedlongitudinally extending opening 57 in which is disposed a core member58. The core member 58 is provided with a centrally located relativelysmall opening 59 which registers with openings 60 and BI of the samesize in the disc 56 and the cup-like member 54, respectively. The coremember 58 is also provided with a concave frusto-conical surface 62which registers with the opening 59 in the core member. The core member58 at its upper end is provided with a large integral ring 63 which hasthe same diameter as the large base of the frusto-conical surface 68 andthe inner surface 64 of the ring 63 abuts the surface 62 in aregistering manner.

Disposed partially within the opening 51 of the coil 63 and above thecore member 58 is a plunger 65. The plunger 65 is of cylindricalconfiguration and is adapted to cooperate with the core member 58 and,the coil 53 to effect the operation of the solenoid. The plunger 65 atits lower end is provided with a reduced portion 66 which has a convexfrusto-conical surface 61 at the lower part of the reduced portion 66and a cylindrical surface 68 disposed between the frusto-conical surface61- and the main portion of the plunger.

The plunger 65 is also provided at its lower end with an axially boredopening 69 which receives one end of a non-magnetic rod I0, the latterextending through the registering openings 59, 60 and 6| in the coremember 58, the disc 56 and the cup-like member 54, respectively. Theother end of the rod I0 is threadedly secured to the plunger extension 4I which engages the ball valve E for effecting operation of thetransmission control system.

It will be seen from the drawings that the concave and convexfrusto-conical surfaces on the core member 58 and the reduced portion 66of the plunger 65, respectively, are parallel and when the plunger 65 isin the position as shown in Fig. 3, the two surfaces form an air gap I00therebetween. Similarly, the surfaces 68 and 64 of the reduced portion66 and core member 58, respectively, form a second air gap I0i. The airgap IOI is only effective when the surface 68 is disposed above thesurface 64. This disposition is shown in Fig. 3. It will be seen thatthe lower edge of the surface 68 is adjacent the upper edge of thesurface 64 and that the distance between these-edges is smaller than thedistance between the frusto-conical surfaces 62 and 61 when the solenoidis in its de-energized condition as shown in Fig. 3. When the coil 53 isenergized a magnetic field is created and flux passed through theopening 57 in the coil. Since the plunger 65 and The flux will, ofcourse, take the.

of flux across the, gap I 0|, the plunger 65, will be urged downwardlytoward the core 58, the force exerted by the magnetic as well as theflux density becoming greater as the gap IOI becomes smaller. When,however, the surface 68 enters within the opening formed by the surface64, there is no longer a sufficient change in the size of the air gap IMand the surfaces around this gap becomes saturated. At this instantduring the movement of the plunger, the fiux changes and bridges the gapI00 and as the gap I00 gets smaller the flux density increases as wellas the force created thereby.

In Fig. 4 I have shown, diagrammatically, the action of my improved,solenoid. Curve A illustrates the force-stroke relationship of aconventional solenoid having only one air gap. In curve A, theforce'steadily increases as. the stroke: increases, due to the fact thatthe flux density: becomes greater as the air gap becomes smaller.v Incurve B I have shown the force-stroke relationship of my improvedstructure. The initial rise shown at I50 is caused by the effect ofthe-air gap IllI while the subsequent rise I5I is caused by the finalmovement of the plunger 65. under the influence of the magnetic fluxbridging the gap I00. By the construction shown, a greater initial forceis exerted by the plunger 65 as well as its extension compared to theconventional type illustrated by curve A in Fig. 4..

While I have illustrated and described butone cave frusto-conioalopening in said first core member, and a second core member disposed insaid opening having a reduced portion provided with a convexfrusto-conical surface forming; an air gap with and parallel to saidfrusto-conical opening, said reduced portion of said second core memberat the largerv end of said convex surface terminating in a cylindricalsurface, the juncture of said convex surface. and said cylindricalsurface of said reduced portion and the inner. lateral edge of saidringbeing. juxtaposed when. said.op.-- erator is de-energized to therebyeffect, the. pas

sage of a greater amount of magnetic flux. be.-

tween said last mentioned surfaces than between said frusto-conicalsurfaces whensaid operator is initially energized.

LOUIS B. FORMAN.

REFERENCES CITED The following references are of record in-the. file ofthis patent:

UNITED STATES, PATENTS Number Name Date 1,460,517 Stevens July 3, 1923.2,076,858 Morgenstern Apr. 13, 1937 2,330,407 Claytor Sept. 28, 19432,407,603 Derungs Sept. 10, 1946 OTHER REFERENCES Magnets, by C. R.Underhill, pages 67, 68and;

69, McGraw Hill Book Co., Inc., New York, 1924.

